Thermal balance in man during 24 h in controlled environment

Abstract

Evaporative, radiant and convective heat losses, metabolism and heat storage were determined on 8 unclothed reclining fasting subjects during 24 h in a climatic chamber maintained at a strictly constant and neutral temperature. In these conditions, a basal evolution of the body heat content and the rectal temperature were observed with nearly a disappearance of the diurnal thermal increase but persistency of a nocturnal falling followed by an early moring increase. Nocturnal cooling could be linked essentially with a rising skin temperature very likely through skin vasodilatation. Thus, the increase in radiant and convective heat losses was initially, constantly and predominantly involved for cooling the body in the evening and at night. The part played by the various skin areas was variable with the time, hands and feet temperature varying paradoxically in an opposite way to temperatures in other skin areas. Effects of an increase in evaporation and a decrease in basal metabolic rate were added later on but less systematically.